Balloon expandable stent with a self-expanding portion

ABSTRACT

A stent consisting of at least two parts in juxtaposition, one part being of self-expandable characteristics while the other part is balloon expandable.

FIELD OF THE INVENTION

The present invention relates to a new type of stent for transluminalimplantation and in particular new vascular stents.

BACKGROUND OF THE INVENTION

Stents for transluminal implantation are well known. They are generallycomprised of metallic supports which are inserted into a part of thehuman body such as bile ducts, the urinary system, the digestive tubeand notably by percutaneous route inside the blood vessels, usually thearteries in which case they are typically termed vascular stents. Stentsare usually generally cylindrical and are constructed and arranged toexpand radially once in position within the body. They are usuallyinserted while they have a first relatively small diameter and implantedin a desired area, for example inside a vessel, then the stent isexpanded in situ until it reaches a second diameter larger than thefirst diameter. A balloon associated with the catheter is usually usedto provide the necessary interior radial force to the stent to cause itto expand radially. Self-expanding stents are also known which canexpand from a first diameter to a larger second diameter without the useof a means for applying an interior radial force, such as a balloon, tothem. One such type of self-expanding stent is a stent made of a shapememory metal which expands to its second larger diameter upon exposureto body temperature. Such stents are also known.

SUMMARY OF THE INVENTION

The present invention proposes a novel type of stent which combines aself-expanding part or portion with a part or portion which requires aninterior radial force for expansion. More specifically, a stent fortransluminal implantation according to the present invention willcomprise cylindrical parts preferably in juxtaposition, with at leastone part being self-expanding whereas another part requires an interiorradial force for its expansion, such as a balloon catheter or the like.Basically, the stent will consist of at least two of the aforementionedparts but may consist of more than two parts. Such an arrangementenables improved placement of the stent by providing immediate expansionin part upon release of the stent from its delivery catheter.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a showing of one embodiment of a stent according to thisinvention;

FIG. 2 is a schematic showing of a stent similar to that of FIG. 1 on adelivery catheter;

FIG. 3 is a schematic showing of the delivery system of FIG. 2 with thestent released for implantation;

FIGS. 4 and 5 are schematic-showings of a stent of the invention used ina vessel branching situation; and

FIG. 6 is a showing of another embodiment of a stent according to theinvention, and

FIGS. 7-10 are schematic showings of bifurcated stents making use of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a stent which combines self-expanding characteristics andballoon expandable characteristics, i.e., requires expansion by use of aradial interior force. Preferably, the stent will have theself-expanding part 12 joined at one end in juxtaposition to theproximal end of a balloon expandable stent 14. The parts of the stentmay be formed in accordance with any of the known stents extant in theprior art. Preferably however, the self-expanding part 12 will be of ashape memory metal such as nitinol so as to enable self-expansion atbody temperature upon release of the stent from its delivery catheter(not shown). The immediate expansion of part 12 aids in placement of thestent during release, following which a balloon or the like may be usedto expand part 14.

Part 12 may be of a larger diameter, or it may be flared. to provide theearliest possible contact with the body portion into which it isinserted, such as a vessel. This is best seen for example in FIGS. 2 and3 which show a stent 10 similar to that of FIG. 1 on a deliverycatheter. FIG. 2 shows the stent having the two parts 12 and 14,respectively. Part 12 is the self-expanding part while part 14 requiresa separate force for expansion such as a balloon 16 of a deliverycatheter generally indicated at 18 inside the stent. In FIG. 2, thestent is shown prior to release or deployment, the self-expanding partis enclosed by a retractable sheath 20. In FIG. 3, the sheath has beenretracted, allowing self-expanding part 12 to flare-outwardly.Subsequently, balloon 16 may be used in the known manner to expand part14.

Since most stent delivery catheters include a retractable sheath whichexposes the stent for implantation and removal from the catheter, if theself-expanding part 12 is placed on the proximal end of the stent asshown, it will most likely be able to lock the stent in place until theremainder of the stent is expanded as by balloon expansion. Thisplacement is preferable although placement in other parts of the stentproper may also be used.

When the self-expanding portion is placed at the proximal end of thestent, such a stent is particularly useful in vessel stenting in whichthe vessel is of the bifurcating or branching type. Such a stent isshown schematically in FIGS. 4 and 5 at 10. FIG. 4 shows the stenthaving a proximal end part 12 which is self-expanding while theremainder of the stent body 14 is balloon expandable by balloon 16 oncatheter 18. In FIG. 4, the retractable sheath has been removed allowingthe self-expanding part to expand at the ostium 22 in a vessel 24branching off of a main vessel such as aorta 26, helping to moreaccurately place the stent. FIG. 5 shows the stent after expansion ofpart 14 by the balloon catheter and catheter retraction. A stentaccording to the present invention allows positive placement of thestent near the ostium of the bifurcation.

Stents according to the invention may also be comprised of more than oneself-expanding and one balloon expandable part. Any combination of theseparts is deemed to be within the scope of this invention. For example,referring to FIG. 6, a stent 10 is shown having a self-expanding part 12at each end of a balloon expandable part 14.

Referring now to FIGS. 7-10, bifurcated stents making use of theinvention are described. Generally, bifurcated stents consist of threesegments or components, a main trunk and two branches. In making use ofthis invention, any of the three components may be made to be balloonexpandable or self-expandable, as desired. For example, FIG. 7 shows anunexpanded bifurcated stent 10 of one configuration in schematic formhaving a trunk 30, a first branch 32 and a second branch 34. As shown,trunk 30 is self-expanding, such as part 12 in the earlier Figures, andbranches 32 and 34 are balloon expandable, such as part 14 in theearlier Figures.

FIG. 8 shows the stent of FIG. 7 in an implanted position in a branchingvessel 36.

FIG. 9 shows another example of an unexpanded bifurcated stent 10 ofanother configuration in schematic form consisting of trunk 30 andbranches 32 and 34. In this case, trunk 30 and branch 23 are bothself-expanding and branch 34 is balloon expandable.

FIG. 10 shows the stent of FIG. 9 expanded in an implanted position in abranching vessel 36.

Trunk 30 in another embodiment may be balloon expandable while thebranches 32 and 34 may be self-expandable.

The above Examples and disclosure are intended to be illustrative andnot exhaustive. These examples and description will suggest manyvariations and alternatives to one of ordinary skill in this art. Allthese alternatives and variations are intended to be included within thescope of the attached claims. Those familiar with the art may recognizeother equivalents to the specific embodiments described herein whichequivalents are also intended to be encompassed by the claims attachedhereto.

1-15. (canceled)
 16. A stent having a length and comprising at least oneself expanding portion and at least one balloon expandable portion, inan unexpanded state the stent has a diameter that is substantiallyuniform along the length of the stent, in an expanded state the stenthas a first section and a second section wherein the second section hasa diameter greater than that of the first section.
 17. The stent ofclaim 16 wherein the first section is balloon expandable and the secondsection is self expanding.
 18. The stent of claim 16 having a proximalend region, a distal end region and a medial region there between,wherein the second section comprises at least a portion of the proximalend region.
 19. The stent of claim 18 wherein the first section isballoon expandable and the second section is self expanding.
 20. Thestent of claim 18 wherein in the expanded state the proximal end regionflares radially outward from the medial portion.
 21. The stent of claim20 wherein the proximal end region flares out radially such that aproximal most portion of the proximal end region has a substantiallygreater diameter than that of a distal most portion of the proximal endregion.
 22. The stent of claim 16 having a proximal end region, a distalend region and a medial region there between, wherein the second sectioncomprises at least a portion of the distal end region.
 23. The stent ofclaim 22 wherein the first section is balloon expandable and the secondsection is self expanding.
 24. The stent of claim 22 wherein in theexpanded state the distal end region flares radially outward from themedial portion.
 25. The stent of claim 24 wherein the distal end regionflares out radially such that a distal most portion of the distal endregion has a substantially greater diameter than that of a proximal mostportion of the distal end region.
 26. The stent of claim 16 wherein atleast a portion of the stent is made of nitinol.
 27. The stent of claim16 wherein at least a portion of the second section is made of nitinol.28. The stent of claim 16 wherein the second section is shorter than thefirst section.
 29. A stent having a length and comprising at least oneself expanding portion and at least one balloon expandable portion, inan unexpanded state the stent has a diameter that is substantially thesame along the length of the stent, in an expanded state the at leastone self expanding portion has a diameter greater than that of the atleast one balloon expandable portion.
 30. The stent of claim 29 whereinthe at least one self expanding section is at an end of the stent. 31.The stent of claim 29 having a proximal end region, a distal end regionand a medial region there between, wherein the proximal end region andthe distal end region are self expanding such that in an expanded stateat least one of the end regions has a diameter greater than that of themedial region.